A lawyer for two of the five men accused of raping and killing an Indian trainee physiotherapist says a prosecution witness has identified all the defendants.
The five had pleaded not guilty to charges that they raped and murdered the 23-year-old woman.
The case has led to a shake-up of laws against sexual crimes after protests about the rising number of attacks on women.
Police say the gang lured the woman onto a bus in New Delhi, where they repeatedly raped and assaulted her with a metal bar before throwing her bleeding onto a highway.
She died of internal injuries two weeks after the 16 December attack.
Lawyers said the men face 13 charges including murder, which carries a maximum penalty of death.
Today's proceedings marked the start of the trial, although the men formally pleaded not guilty to the charges on Saturday 2 February.
AP Singh, a lawyer defending two of the accused, Vinay Sharma and Akshay Thakur, told the media that a leading prosecution witness had identified all five men, the bus on which the attack was alleged to have taken place and some of the victim's belongings.
Mr Singh said the defence lawyers would begin cross-examining the defendant tomorrow.
The prosecution says it has strong evidence against the five men including blood stained clothing, DNA matches, mobile phone records, confessions and eye-witness statements.
A sixth person police say was part of the gang that attacked the woman and her friend is a juvenile and will be tried separately.
Under new rules, due to be signed into law by the president in the coming days, gang rape that leads to death will be punishable by death while minimum penalties will be raised to 20 years for gang rape and rape of a minor.
The laws must later be ratified by parliament.